AC generator for motor vehicles

1. An AC generator for a motor vehicle, the AC generator comprising: a rotor fitted over a shaft rotatably supported within a casing; a stator attached to said casing to surround said rotor; and a rectifier having a positive-polarity side cooling plate, positive-polarity side one-way conducting devices mounted on a fitting surface of said positive-polarity side cooling plate, a negative-polarity side cooling plate and negative-polarity side one-way conducting devices mounted on a fitting surface of said negative-polarity side cooling plate, said rectifier being fixedly tightened with a fitting screw to said casing in a state where a direct-fitting surface of only one of either said positive-polarity side and said negative-polarity side cooling plates opposite to said fitting surface thereof is brought closely into contact with a casing direct-fitting surface formed on an inner wall surface of said casing and the other of said positive-polarity side and said negative-polarity side cooling plates is not brought closely into contact with said casing direct-fitting surface; wherein an intervening member providing thermal conductivity is interposed between said direct-fitting surface of said only one of either said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface to cover at least an area right under said one-way conducting devices mounted on said fitting surface of said only one of either said positive-polarity side cooling plate and said negative-polarity side cooling plate to constitute an electric conducting portion at which said direct-fitting surface of said only one of either said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface come directly into contact with each other and a thermal conducting portion at which said direct-fitting surface of said only one of either said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface come into contact with each other in a state where said intervening member is interposed therebetween.

2. An AC generator for a motor vehicle as defined in claim 1, wherein said intervening member is interposed between said direct-fitting surface of said one of said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface so that said thermal conducting portion surrounds said electric conducting portion.

3. An AC generator for a motor vehicle as defined in claim 1, further comprising an intervening member accommodating groove for accommodating said intervening member provided in at least one of said direct-fitting surface of said one of said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface.

4. An AC generator for a motor vehicle as defined in claim 3, further comprising an intervening member clearance groove made in at least one of said direct-fitting surface of said one of said positive-polarity side cooling plate and said negative-polarity side cooling plate and said casing direct-fitting surface so as to constitute a boundary between said thermal conducting portion and said electric conducting portion.

5. An AC generator for a motor vehicle as defined in claim 1, wherein said intervening member is made from a sheet-like material.

6. An AC generator for a motor vehicle as defined in claim 1, wherein said intervening member is made out of a grease-like material.

7. An AC generator as claimed in claim 1, wherein said thermally conductive silicone intervening member has a thermal conductivity of at least 2.5 kcal/mh .degree.C.

8. An AC generator comprising; a rotor fitted over a shaft rotatably supported within a casing; a stator attached to said casing to surround said rotor; and a rectifier having a positive-polarity side cooling plate with a plurality of positive-polarity side one-way conducting devices mounted on a fitting surface of said positive-polarity side cooling plate, a negative-polarity side cooling plate with negative-polarity side one-way conducting devices mounted on a fitting surface of said negative-polarity side cooling plate, said rectifier being attached with a fitting screw to said casing whereby a direct-fitting surface of only one of either said positive-polarity side and said negative-polarity side cooling plates opposite to said fitting surface is brought closely into contact with a casing direct-fitting surface formed on an inner wall surface of said casing; wherein a thermally conductive silicone intervening member is interposed between said direct-fitting surface of the one cooling plate brought closely into contact with said casing direct-fitting surface and said casing direct-fitting surface to cover at least an area directly under respective said one-way conducting devices mounted on said fitting surface of the one cooling plate brought closely into contact with said casing direct-fitting surface to constitute an electric conducting portion in an area where said direct-fitting surface of the one cooling plate brought closely into contact with said casing direct-fitting sure and said casing direct-fitting surface come directly into contact with each other and a thermal conducting portion in an area where said direct-fitting surface of the one cooling plate brought closely into contact with said casing direct-fitting surface and said casing direct-fitting surface come closely into contact with each other with said thermally conductive silicone intervening member interposed therebetween.